JP3790178B2 - Intra / inter determination method in video encoding, video encoding apparatus, video encoding program, and recording medium for the program - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
In video coding, whether to encode a macroblock to be encoded as an intra macroblock without prediction from another macroblock or an inter macroblock with prediction from another macroblock This determination should be made in consideration of the effect on image quality.
[0002]
The present invention relates to coding control of video coding, and in particular, by color difference SAD of a macroblock in video coding for determining whether a macroblock to be coded should be coded with an intra macroblock or an inter macroblock. The present invention relates to an intra / inter determination method in video encoding, a video encoding device, a video encoding program, and a recording medium for the program.
[0003]
[Prior art]
A verification model ver. Stipulated in MPEG-4, an international standard for video coding. 16 (VM16) encoding control, the intra / inter determination for determining whether the encoding target macroblock in the P-VOP is encoded as an intra macroblock or an inter macroblock (mode) As the prediction generated code amount when the encoding target macroblock is encoded as the intra macroblock, the MAD of the luminance value Y of the pixel in the encoding target macroblock (the average value of the pixel values in the macroblock and each pixel value) The sum of the absolute values of the difference between the two values is used as a predicted generated code amount when encoded as an inter-macroblock, and the SAD of the luminance value Y of the pixel (the predicted image created from the motion vector calculated in advance and the pixel value of the original image) The sum of the absolute values of the differences is used, and the type with the smaller predicted code amount is used by comparing the values. Which was.
[0004]
FIG. 4 is a diagram for explaining an example of a conventional intra / inter determination method. In the intra / inter determination unit 60 in the conventional video encoding, the luminance value determination unit 11 calculates the MAD of the luminance value Y of the pixel in the encoding target macroblock of the input P-VOP and the SAD of the luminance value Y. When the magnitude comparison process is performed and the MAD of the luminance value Y is smaller than the SAD of the luminance value Y, specifically, the MAD value A _y of the luminance value Y is obtained from the SAD value SAD _inter of the luminance value Y. is smaller than minus the predetermined value 2 * N _B determines the coding target macroblock and the intra macroblock, in other cases, determines that the inter macroblock.
[0005]
“MPEG-4”, “VM16”, “P-VOP”, “macroblock”, “intra macroblock”, “intermacroblock”, “intra / inter determination”, “motion vector”, “MAD” , “SAD” is described in the following documents 1 and 2.
Reference 1: “All about MPEG-4”, pp. 37-116, written by Junichi Miki, Industrial Research Committee.
Reference 2: “ISO / IEC JTC1 / SC29 / WG11: MPEG-4 Video Verification Model version 16.0”, Shigeru Fukunaga et al., Pp. 48-50, March, 2000 ”.
[0006]
[Problems to be solved by the invention]
In a general MPEG encoding system, many means are used to reduce color difference information by utilizing the fact that humans are not sensitive to color. In MPEG-4, which is one of the video encoding systems targeted by the present invention, the color difference information is reduced by half in the vertical and horizontal directions, so the information amount of the color difference information is one of the information amount of the luminance information. / 4. Therefore, it can be said that the information that greatly affects the generated code amount is luminance information.
[0007]
In the conventional intra / inter determination of macroblocks, the mode is determined by comparing the size of the predicted generated code when encoded as an intramacroblock and when encoded with an intermacroblock. Only luminance values with a large amount of information were used to predict the amount.
[0008]
Therefore, when intra / inter determination is performed by the conventional method described with reference to FIG. 4, even if the error of the color difference value becomes large, this is not taken into consideration at all, and the inter determination is made only by the determination based on the luminance value information. In many cases, the sticking of color remains visually.
[0009]
That is, as a problem of the determination method according to the prior art, for example, when the motion vector is not properly calculated and the SAD of the luminance value Y becomes a smaller value, in the intra / inter determination, Since it is determined as an inter-macroblock, there is actually a phenomenon in which the difference between one of the two color difference values U and V remains in the screen as a color sticking. This is a phenomenon that often occurs in an image in which an object including many of the color difference values U and V moves violently in the screen.
[0010]
Such a macroblock needs to be encoded as an intra macroblock. However, in the conventional determination method, such a phenomenon cannot be avoided for determination using only the luminance value Y. could not.
[0011]
An object of the present invention is to perform intra / inter determination of a macroblock in order to suppress a color sticking phenomenon in video coding.
[0012]
[Means for Solving the Problems]
In order to solve the above-described problem, the present invention further provides a method for determining the MAD of the luminance value Y and the SAD of the luminance value Y in the intra / inter determination of the encoding target macroblock. In the two color difference values U and V, MAD and SAD are calculated, and processing for intra / inter determination is added again.
[0013]
That is, in the conventional intra / inter determination, MAD and SAD are further calculated for the two color difference values U and V in the encoding target macroblock for the encoding target macroblock determined as the inter macroblock. Compare the size. When the value obtained by subtracting the weighting coefficient from any of the SADs is larger than MAD, the prediction error of the encoding target macroblock is considered to be large, and processing for re-determination is added to the intra macroblock. .
[0014]
It differs greatly from the prior art in that the two color difference values U and V are used for the determination in addition to the determination by the luminance value Y of the pixel in the macroblock for the intra / inter determination of the macroblock.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described. FIG. 1 is a diagram showing the basic configuration of an embodiment of the present invention. In FIG. 1, reference numeral 10 denotes an intra / inter-determining whether a macro block is encoded as an intra macro block or an inter macro block in video encoding. A determination unit 11 represents luminance value determination means, and 12 represents color difference value determination means.
[0016]
The luminance value determination unit 11 is the same as the luminance value determination unit 61 in the conventional intra / inter determination unit 60 shown in FIG. 4, and the luminance value Y of the pixel in the macroblock to be encoded of the input P-VOP. A size comparison process is performed between the MAD and the SAD of the luminance value Y.
[0017]
When the MAD of the luminance value Y is smaller than the SAD of the luminance value Y, specifically, the MAD value A _y of the luminance value Y is a predetermined value 2 * N from the SAD value SAD _inter of the luminance value Y. If it is smaller than the value obtained by subtracting _B , the encoding target macroblock is determined to be an intra macroblock, and the intra / inter determination process is terminated. Otherwise, the process to the color difference value determination means 12 is performed. Deliver.
[0018]
The color difference value determination means 12 performs a size comparison process between the SAD of the color difference value U and the MAD of the color difference value U, and a size comparison process of the SAD of the color difference value V and the MAD of the color difference value V in the encoding target macroblock. . When the value obtained by subtracting the weighting coefficient OM from the SAD value SAD _u of the color difference value U is larger than the MAD value A _u of the color difference value U, or the weight from the SAD value SAD _v of the color difference value V If the value obtained by subtracting the coefficient OM association is greater than the value a _v of MAD chrominance value V is a the coding target macroblock is determined that the intra-macro block, determines that inter macroblock otherwise Then, the intra / inter determination process is terminated.
[0019]
Incidentally, the N _B and weighting coefficients OM is such determine the appropriate value by an experiment using a pre various sample images. In the above example, the relational expression between the R, G, and B signals, the luminance signal Y, and the color difference signals U and V is as follows (see ITU-R BT Rec. 601).
[0020]
Y = 0.299R + 0.587G + 0.114B
U = R−Y = 0.701R−0.587G−0.114B
V = B−Y = −0.299R−0.587G + 0.886B
FIG. 2 is a block diagram of an MPEG-4 encoder to which the present invention is applied, and FIG. 3 is a processing flow diagram thereof. In FIG. 2, 10 is an intra / inter determination unit, 20 is a DCT / quantization processing unit, 30 is an inverse quantization / IDCT processing unit, 40 is a frame memory storage unit, and 50 is a motion compensation processing unit.
[0021]
Hereinafter, application examples of the present invention will be described with reference to FIGS. In step S1, it is determined whether or not the frame type is I-VOP for the input image. If the frame type is I-VOP, the process proceeds to step S5, and intra macroblock encoding processing (DCT processing, quantization processing) by the DCT / quantization processing unit 20 is performed. If the frame type is not I-VOP, step S2 is performed. Proceed to
[0022]
In step S2, it is determined whether or not the frame type is P-VOP. If it is not P-VOP but B-VOP, the process proceeds to step S4. If the frame type is P-VOP, intra / inter determination processing by the intra / inter determination unit 10 is performed in step S3. Here, if the intra / inter determination processing described in FIG. 1 is performed and the determination result is an inter macroblock, the inter macroblock encoding processing (DCT processing, quantization) by the DCT / quantization processing unit 20 is performed in step S4. Process). If the determination result is an intra macroblock, intra macroblock encoding processing (DCT processing, quantization processing) by the DCT / quantization processing unit 20 is performed in step S5.
[0023]
The encoded data generated by each encoding process is subjected to an inverse quantization process and an IDCT process by the inverse quantization / IDCT processing unit 30 in step S6, and is stored in the frame memory by the frame memory storage unit 40 in step S7. In step S8, motion compensation processing by the motion compensation processing unit 50 is performed and reused in subsequent frames.
[0024]
The above processing can be realized by a dedicated processor or hardware circuit, and can also be realized by a general-purpose computer and a software program, such as a computer-readable portable medium memory, semiconductor memory, hard disk, etc. It can be executed by a computer by storing it in an appropriate recording medium and reading it from there. The program can be downloaded from another computer via a communication line, and can be installed and executed.
[0025]
【The invention's effect】
As described above, according to the present invention, the color sticking that occurs when the motion vector is not correctly calculated by the intra / inter determination process using the two color difference values U and V of the pixels in the macroblock. This makes it possible to avoid the phenomenon and greatly suppress the deterioration of image quality.
[Brief description of the drawings]
FIG. 1 is a diagram showing a principle configuration of an embodiment of the present invention.
FIG. 2 is a block diagram of an MPEG-4 encoder to which the present invention is applied.
FIG. 3 is a processing flowchart of an MPEG-4 encoder to which the present invention is applied.
FIG. 4 is a diagram for explaining an example of a conventional intra / inter determination method;
[Explanation of symbols]
10, 60 Intra / inter determination unit 11, 61 Luminance value determination unit 12 Color difference value determination unit 20 DCT / quantization processing unit 30 Inverse quantization / IDCT processing unit 40 Frame memory storage unit 50 Motion compensation processing unit

Claims (4)

An intra / inter determination method for determining whether a macro block is encoded as an intra macro block or an inter macro block in video encoding,
With respect to a macroblock that is determined to be an inter macroblock by the intra / inter determination based on the luminance value Y of the pixel in the encoding target macroblock, SAD is further used for two color difference values U and V of the pixel in the macroblock. , MAD is calculated, and when a value obtained by subtracting a predetermined weighting coefficient from any of the SADs is larger than the corresponding MAD of the color difference value, the macroblock is determined to be an intra macroblock. An intra / inter determination method in video coding characterized by correcting. In a video encoding device having an intra / inter determination unit that determines whether a macro block is encoded as an intra macro block or an inter macro block in video encoding,
The intra / inter determination unit
Luminance value determining means for performing intra / inter determination based on the luminance value Y of the pixel in the encoding target macroblock;
SAD and MAD are calculated for each of the two color difference values U and V of the pixels in the macro block for the macro block determined to be an inter macro block by the luminance value determination means, and predetermined from either SAD. And a color difference value determining means for determining that the macroblock is an intra macroblock when the value obtained by subtracting the weighting coefficient of the image is larger than the MAD of the corresponding color difference value. Encoding device. A program for determining by a computer whether a macro block is encoded as an intra macro block or an inter macro block in video encoding,
A process of performing intra / inter determination based on the luminance value Y of the pixel in the encoding target macroblock;
A process of calculating SAD and MAD for the two color difference values U and V of the pixels in the macroblock for the macroblock determined as the inter macroblock by the intra / inter determination;
Based on the calculation result, when a value obtained by subtracting a predetermined weighting coefficient from any one of the SADs is larger than the corresponding MAD of the color difference value, the macroblock is determined again as an intra macroblock. Processing,
A video encoding program to be executed by a computer. A recording medium recording a program for determining by a computer whether to encode a macro block as an intra macro block or an inter macro block in video encoding,
A process of performing intra / inter determination based on the luminance value Y of the pixel in the encoding target macroblock;
A process of calculating SAD and MAD for the two color difference values U and V of the pixels in the macroblock for the macroblock determined as the inter macroblock by the intra / inter determination;
Based on the calculation result, when a value obtained by subtracting a predetermined weighting coefficient from any one of the SADs is larger than the corresponding MAD of the color difference value, the macroblock is determined again as an intra macroblock. Processing,
A recording medium for a video encoding program, wherein a program for causing a computer to execute is recorded.

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